joe fryer, nbc news, los angeles. >> we are eping a close eye on the possibility of severe weather in the middle of the country. the area extends from e great lakes to the midouth. severe thunderstorms, damaging wis and tornadoes are s able. the threat will move from west to east througut the day tomorrow. when "nbc nightly news" continues onhe this saturday, what's become an almost unbearable situation f one town that fis itself a magnet for those unwantedisitors. >>> later the inspiring story of a young man who is running fast beuse his time with those loves may be lited. >>> we are back with atory that gives new meaning to the problem ofnbearable neighbors. we are tking about polar bea that invade a northern canada town for years and have done so wi a vengeance this ye. it may have to do with climate chge. we get the story from nbc's chief environmental affairs correspondent, anne thpson. >> reporter: where the polar bes roam in churchill, canada, the street signsre a little different. here, 800 people and some 900 bears try to co-exist from late june to late novber when the sea ic